DENVER (KDVR) — One of the first COVID-19 patients in Colorado to receive an experimental treatment has died after suffering multiple strokes. Scott Kaplan was the recipient of a convalescent plasma treatment in early April. The 43-year-old spent 40 days in the hospital, according to his sisters.

“The worst roller coaster ride. He would have a good day and you’d take a sigh of relief and then the next morning something happened overnight and he took two steps back,” said Marci Kaplan, one of Scott’s sisters.

A small funeral was held for Scott Wednesday. His sister, Samantha Dunham lives out of state and was not able to be there in person.

“It still doesn’t seem real. Yes, we buried him but I don’t feel like he’s actually gone, if that makes any sense,” said Dunham.

The two say Scott showed signs of improvement after receiving the convalescent plasma treatment. Just before he died, they say he was off the ventilator and was working with therapists.

“We had created a playlist for him so he could listen to his music and when one of the nurses came back in, he was actually mouthing the words to the songs. So his brain was coming back to us,” said Kaplan.

A series of blood clots ultimately led to two strokes from which Scott could not recover. Blood clotting is a symptom that physicians say can appear in COVID-19 patients, especially severe cases.

“It’s not the most common symptom of COVID and it tends to, at least in the patients we’ve seen, present after they had their most significant symptoms of COVID,” said Dr. Barbara Melendez, a vascular surgeon at Vascular Institute of the Rockies.

Melendez says studies show 17 to 30 percent of COVID-19 patients will develop some kind of cardiovascular complication. She says the virus creates an inflammatory response, damaging the inside of the arteries and blood vessels and causing the blood to thicken.

“If the inside of our arteries are not working as they should, the blood gets into a stalled pattern and that stalled pattern can cause clots,” said Melendez.

Scott’s family is now left trying to imagine a world without the man known as a gentle giant. In the wake of his death, they urge others to take the disease seriously.

“It’s very real. If you don’t take it seriously, it’s going to happen to someone you know and love,” said Dunham.